Apparatus and reactor for generating and feeding high purity moisture

ABSTRACT

A safe, reduced pressure apparatus for generating water vapor from hydrogen and oxygen and feeding high purity moisture to processes such as semiconductor production. The apparatus eliminates the possibility of the gas igniting by maintaining the internal pressure of the catalytic reactor for generating moisture at a high level while supplying moisture gas from the reactor under reduced pressure. A heat dissipation reactor improvement substantially increases moisture generation without being an enlargement in size by efficient cooling of the reactor alumite-treated fins.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to and claims the early filing date ofJapanese patent applications JP11-223548, filed Aug. 6, 1999;JP11-338882, filed Nov. 30, 1999; and PCT application JP00/04911, filedJul. 21, 2000. The entire disclosures of the above applications arehereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to an apparatus for generating and feedingwater-vapor, hereinafter referred to as moisture, and amoisture-generating catalytic reactor for use in the apparatus employedin the production of semi-conductors. More specifically, the presentinvention relates to a reduced pressure apparatus for generating andfeeding moisture in which moisture gas is supplied under reducedpressure to the downstream side of the reactor while maintaining anelevated internal pressure in the portion of the reactor for generatingmoisture. The configuration thereby prevents hydrogen from spontaneouslyigniting in the reactor. The invention includes a heat dissipation-typereactor for generating moisture in which heat generated in the moisturegenerating reaction is forced to dissipate through fins, increasing thequantity of moisture generated within a safe temperature range.

BACKGROUND OF THE INVENTION

Silicon oxide film formation by moisture oxidation, for example, canneed more than 1,000 sccm or cubic centimeters/minute of high-puritywater in a standard state in semiconductor manufacturing. For thatpurpose, the inventors earlier developed and disclosed reactors forgenerating high purity moisture as shown in FIG. 5 and FIG. 6.

The reactor shell 1 shown in FIG. 5 is formed by mating a reactorstructural component 2 on the inlet side having a material gas supplyjoint 9 and a reactor structural component 3 on the outlet side having amoisture gas take-out joint 12. In the reactor shell 1, a reflector 8 onthe inlet side is so clamped by screw bolts 5 as to face a material gassupply passage 7 and a reflector 11 on the outlet side to face amoisture gas outlet passage 10.

The inside wall surface of the reactor structural component 3 on theoutlet side is provided with a platinum coated catalyst layer 13. Theinside wall surface of the reactor structural component 2 on the inletside and the outside surfaces of the reflector 8 on the inlet side andthe reflector 11 on the outlet side are provided with a barrier coat 13a formed of a nitride such as TiN which will be described later.

The platinum coated catalyst layer 13 is formed on the barrier coat 13 aof a nitride like TiN provided on the inside wall of the reactorstructural component 3 on the outlet side by fixing the platinum coat 13b by vapor deposition technique, ion plating technique or the like.

In the reactor shell 1 shown in FIG. 6, there is provided a relativelythick reflector 22, and the inside surface of the reactor structuralcomponent 3 on the outlet side is provided with a platinum coatedcatalyst layer 13 formed of barrier coat 13 a and platinum coat 13 b.

The inside surface of the reactor structural component 2 on the inletside and the outside surface of reflector 22 are provided with barriercoat 13 a but without the platinum coat 13 b described in FIG. 5. Thus,the surfaces of the reactor structural component 2 on the inlet side andreflector 22 are not catalytic, thereby preventing O₂ and H₂ fromreacting on those surfaces and raising the temperature locally.

Referring again to FIG. 5, hydrogen and oxygen, i.e., the materialgases, are fed into the reactor shell 1 through a material gas supplypassage 7 and are diffused in the interior space 6 by the reflector 8 onthe inlet side and the reflector 11 on the outlet side 11 and comes incontact with the platinum coated catalyst layer 13. Upon coming incontact with the platinum coated catalyst layer 13, oxygen and hydrogenare increased in reactivity by the catalytic action of platinum and areturned into the so-called radicalized state. As radicalized, thehydrogen and oxygen instantaneously react into moisture at a temperaturelower than the ignition point of the mixed gas without high-temperaturecombustion. The high purity moisture is then supplied to the downstreamside through the moisture gas outlet passage 10.

Similarly, in the reactor shell 1 shown in FIG. 6, the material gasescomprising hydrogen and oxygen are fed into the reactor shell 1 throughthe material gas supply passage 7 and hit against the reflector 22,diffusing in the interior space 6. The diffused material gases ofhydrogen and oxygen come in contact with the platinum coated catalystlayer 13 and are converted into a radicalized state. As described above,hydrogen and oxygen instantaneously react to produce high puritymoisture without combustion at a high temperature.

The reactor shell 1 of the construction as shown in FIG. 5 and FIG. 6has attracted much attention in the semiconductor manufacturingtechnological field because it permits a substantial size reduction ofthe apparatus used for generating and feeding high purity moisture andcan produce more than 1000 cc/minute in a standard state with a higherreactivity and responsiveness.

Another feature of the reactor shell 1 of FIGS. 5 and 6 is that hydrogenand oxygen are handled at a temperature, e.g., 400° C., at which nospontaneous ignition takes place. Moisture is produced by catalyticreaction alone, and thus high-purity moisture can be secured andsupplied safely.

Furthermore, the inventors have developed a number of techniques toraise the catalytic reaction efficiency in moisture generation accordingto the aforesaid catalytic reaction. To be specific, the inventors haveimproved the structure of the reactor to reduce the remaining hydrogenin the moisture gas by increasing the reaction between hydrogen andoxygen. Also, the inventors have developed a technique for increasingthe reaction between hydrogen and oxygen by gradually increasing theflow rate of hydrogen; and another method of raising the reactionbetween hydrogen and oxygen by starting the supply of hydrogen after thesupply of oxygen while cutting off the supply of hydrogen earlier thanoxygen.

As a result of those techniques, the reactor shell 1 as shown in FIG. 5and FIG. 6 can produce and supply high-purity moisture almost free ofresidual hydrogen.

However, the semiconductor manufacturing line has a large number oftreatment processes in which moisture is fed under reduced pressure, forexample, several Torr. In those processes, hydrogen and oxygen underreduced pressure are fed into the reactor shell 1 from the material gassupply passage 7. Consequently, there is a possibility in those reducedpressure processes that, with the ignition point dropping, hydrogen willspontaneously ignite in the reactor.

FIG. 7 is an ignitability limit curve for a 2:1 (by volume) mixture ofH₂—O₂ in a spherical container with a radius of 7.4 cm. The source ofthe curve is the third edition of a chemical handbook, fundamentals,II-406 published by Maruzen publishing company. The numbers on theordinate indicate the total pressure of the mixed gas while those on theabscissa indicate the ignition temperature.

Assuming from FIG. 7 that when the temperature inside the reactor is setat 400° C. the total pressure of the mixed gas of hydrogen and oxygen isreduced to several Torr. FIG. 7 shows that the ignition point forseveral Torr of pressure is about 400° C. Under this condition, theignition point approaches the set temperature, and hydrogen can ignitespontaneously in the reactor. If the set temperature is still higher,ignition will occur without fail.

As indicated in FIG. 7, the ignition point of hydrogen sharply drops asthe total pressure of the mixed gas of hydrogen and oxygen decreases.Even if the temperature is so set that hydrogen will not ignite when thetotal pressure is high, it can happen that hydrogen will suddenly igniteif the total pressure drops. If hydrogen ignites in the reactor, itsflame flows back toward the upstream side through the material gassupply passage 7 and there is danger that combustion will take place inthe area where hydrogen and oxygen are mixed, melting and breaking thepiping and causing a fire to spread outside the reactor.

Another problem with the reactor of FIGS. 5 and 6 for generatingmoisture is that since the moisture-generating reaction is an exothermicreaction, the generated reaction heat will overheat the whole of thereactor shell 1 and the generated vapor steam. For example, when watervapor is produced at the rate of 1000 cc/minute, the temperature ofwater vapor reaches 400-450° C. because of self-heating. If the moisturegeneration is further increased, the temperature of water vapor willexceed 450° C. and approach the ignition point of hydrogen and oxygen or560° C., bringing about a very dangerous state.

To avoid such a possibility, the upper limit of the moisture generationin the reactor for generating moisture of the prior art construction hasto be 1000 cc/minute in terms of the standard state. One way to increasethe moisture generation is to enlarge the reactor shell 1. But the sizeincrease raises the costs and enlarges the size of the apparatus forgenerating and feeding moisture.

The present invention solves those problems with the prior art reactorand the earlier developed reactors, for generating moisture, including(1) the danger that ignition can occur when the total pressure ofhydrogen and oxygen drops; and (2) moisture generation per unit volumeis limited because the temperature of the reactor for generatingmoisture itself would rise and could cause ignition if the production ofmoisture is increased.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a safe reducedpressure-type apparatus for generating and feeding high purity moisturethat completely eliminates the possibility of the gas igniting when thetotal pressure of the mixture of hydrogen and oxygen drops as mentionedabove. It is another object of the present invention to provide a safereduced pressure-type apparatus for generating and feeding moisture thattotally prevents hydrogen from spontaneously igniting by feedingmoisture gas under reduced pressure, thereby keeping the internalpressure of the reactor for generating moisture at a high level.

It is another object of the present invention to provide aheat-dissipation type reactor for generating moisture that is sodesigned to promote heat dissipation from the outside wall of thereactor so as to completely eliminate the danger of the gas ignitingwhen the moisture generation increases as mentioned above. It is afurther object of the present invention to provide a heat-dissipationtype reactor for generating moisture that is small in size yet canproduce moisture in a large quantity.

Reduced Pressure-type Reactor for Generating Moisture

As set forth above, the apparatus for generating and feeding moistureaccording to the present invention has two objectives to achieve, thatis, (1) to supply high-purity gas under reduced pressure to thedownstream side, and (2) to keep the ignition point of hydrogen at ahigh level by raising the internal pressure in the reactor forgenerating moisture. Ignition is prevented by widening the differencebetween the ignition point and the temperature set for moisturegeneration in the reactor for generating moisture.

After intensive research in trying to solve those problems, theinventors discovered a means to simultaneously achieve the twoobjectives. It was discovered that, if a means for reducing pressure,such as an orifice and valve, are installed on the downstream side ofthe reactor, it is possible to generate moisture gas under a highpressure in the reactor for generating moisture and to supply thegenerated gas under a reduced pressure by squeezing or restricting themoisture gas flow by the means for reducing pressure.

The temperature of the reactor for generating moisture is set at 350°C., for example. If the total pressure of the mixed gas of hydrogen andoxygen is adjusted to 100-1,000 Torr and fed into the reactor forgenerating moisture, the ignition point is 540-580° C. according to FIG.7. The difference between the ignition point and the set temperature is190-230° C. and there is no possibility of hydrogen self-igniting.Keeping the temperature difference wide prevents hydrogen from ignitingand makes it possible to supply moisture gas safely.

One aspect of the invention comprises a reduced pressure-type apparatusfor generating and feeding moisture comprising a reactor for generatingmoisture from hydrogen and oxygen by catalytic reaction and a means forreducing pressure provided on the downstream side of the reactor. Themoisture gas is reduced in pressure by the means for reducing pressureand supplied to the downstream side while, at the same time, theinternal pressure in the reactor is maintained at a high level. Themeans for reducing pressure includes orifices, valves, capillaries orfilters.

In the invention, the reactor for generating moisture comprises areactor shell formed by mating a reactor structural component on theinlet side having a material gas supply joint and a reactor structuralcomponent on the outlet side having a moisture gas take-out joint, areflector on the inlet side so provided in the reactor shell as to facea material gas supply passage, a reflector on the outlet side soprovided in the reactor shell as to face the side of a moisture gasoutlet passage, and a platinum coated catalyst layer provided on theinside wall surface of the reactor structural component on the outletside.

Further, in the invention, the reactor shell is formed by mating areactor structural component on the inlet side having a material gassupply joint and a reactor structural component on the outlet sidehaving a moisture gas take-out joint, a reflector provided in theinterior space of the reactor shell, and a platinum coated catalystlayer provided on the inside wall surface of the reactor structuralcomponent on the outlet side.

Heat Dissipation Type Reactor for Generating Moisture

The inventors have conducted intensive research in seeking to preventexcessive self-heating of the reactor for generating moisture anddiscovered a means for keeping the temperature from rising excessivelyby providing a large number of heat dissipation fins on the outside wallof the reactor used for generating moisture. That discovery made itpossible to raise moisture generation from 1000 cc/minute to 2,000cc/minute without much increasing the size of the reactor for generatingmoisture. Furthermore, the heat dissipation efficiency could be raisedmore when the heat dissipation fins are alumite-treated, and themoisture generation could be furthermore increased up to 2,500cc/minute.

One embodiment of the heat dissipating reactor of the invention providesa reactor shell having an interior space is formed by mating a reactorstructural component on the inlet side and a reactor structuralcomponent on the outlet side, a material gas supply passage provided onthe reactor structural component on the inlet side to supply thematerial gases into the interior space, a material gas supply jointconnected to the material gas supply passage, a moisture gas outletpassage provided on the reactor structural component on the outlet sideto lead out moisture gas from the interior space, a moisture gastake-out joint connected to the moisture gas outlet passage, fin baseplates attached firmly on the outside wall of the reactor structuralcomponents and a large number of fins set up on the fin base plates. Thefin base plate may be attached firmly on the outside wall of the reactorstructural components with a heater and a heater press plate placedbetween.

In a further embodiment of the invention, the aforesaid heat dissipationfins are disposed central-symmetrically or axial-symmetrically with thematerial gas supply joint or the moisture gas take-out joint serving ascenter.

In another embodiment of the invention, the heat dissipation efficiencyis improved by providing an alumite treatment to the surfaces of theheat dissipation fins.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an embodiment of a reducedpressure-type apparatus for generating and feeding moisture according tothe present invention.

FIG. 2 is a graph showing the dependence of the pressure of the reactorfor generating moisture on N₂ gas flow rate.

FIG. 3 is a graph showing the dependence of the pressure of the reactorfor generating moisture on the flow rate of the mixed gas of H₂—O₂.

FIG. 4 is a graph showing the concentration of unreacted H₂ gas whilethe flow rate of O₂ gas changes as in FIG. 3.

FIG. 5 is a sectional view of an earlier developed example of thereactor for generating moisture.

FIG. 6 is a sectional view of another earlier developed examp1e of thereactor for generating moisture.

FIG. 7 is an ignitability limit (prior art) of a 2:1 (by volume) mixtureof H₂—O₂.

FIG. 8 is a vertical, sectional view of the reactor shell of the reactorfor generating moisture according to the present invention.

FIG. 9 is a top view of the heat dissipation unit according to thepresent invention.

FIG. 10 is a sectional view taken on line I-I in FIG. 2.

FIG. 11 is a side view of the reactor for generating moisture with theheat dissipation unit clamped on the reactor structural component on theinlet side.

FIG. 12 is an end view of the reactor structural component on the outletside.

LIST OF REFERENCE LETTERS AND NUMERALS FOR THE DRAWINGS

BA baking area C process chamber F filter M mass analyzer MFC 1-3 massflow controllers MFC P1, P2 pressure detectors R recorder RM pressurereducing means RP vacuum pump S1, S2 hydrogen sensors SV sampling valvesV1-V11 valve WVG reactor for generating moisture 1 reactor shell 2reactor structural component on the inlet side 2a recess 3 reactorstructural component on the outlet side 3a recess 4 weld 5 screw bolt 6interior space 7 material gas supply passage 8 reflector on the inletside 9 material gas supply joint 10 moisture gas outlet passage 11reflector on the outlet side 12 moisture gas take-out joint 13 platinumcoated catalyst layer 13a barrier coat 13b platinum coat 14 heatdissipation unit 15 heater 16 heater pressing plate 17 fin base plate 18heat dissipation fins 19 through hole for the joint 20 notch 21 fixingbolt hole 22 reflector P₁-P₃ thermocouples for measurement oftemperature distribution P thermocouple for temperature regulation

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments of the present invention will be described as followswith reference to the drawings, wherein like parts are given thereference numerals.

Embodiments of the Reduced Pressure Apparatus for Generating and FeedingHigh Purity Moisture.

FIG. 1 is a schematic diagram of an embodiment of a reducedpressure-type apparatus for generating and feeding moisture according tothe present invention. From three kinds of gases—H₂, O₂ and N₂—, one ormore gases are chosen by means of V1, V4 and/or V7 and, with the flowrate controlled by mass flow controllers MFC1, MFC2 and/or MFC3, fedinto the reactor WVG for generating moisture through valves V3, V6and/or V9. The valves V2, V5 and V8 are exhaust valves. The details ofthe reactor WVG for generating moisture is omitted in the drawingbecause it is shown in FIGS. 5, 6 or FIG. 8 that will be describedlater. The pressure of moisture gas generated in the reactor WVG forgenerating moisture is measured by a pressure detector P1 and recordedby a recorder R. The moisture gas is squeezed and reduced in pressure bypressure reducing means RM (in FIG. 1, an orifice), and has its residualgas measured by hydrogen sensors S1, S2 and is then sent to a processchamber C via a filter F. The quantity of residual hydrogen is alsorecorded on recorder R.

The gas is heated to 140° C. in the shaded area BA to prevent the gasfrom adsorbing to the inside wall of the pipe.

The moisture gas sent from filter F is sampled by a sampling valve SVand the composition analyzed by a mass analyzer M. The process chamber Cis a, for instance, a semiconductor manufacturing apparatus. The gas isdrawn by a vacuum pump RP via a valve V10 and its internal pressure ismeasured by a pressure gauge P2. Unnecessary gas is discharged through avalve V11.

The pressure of the material gases flowing in mass flow controllersMFC1-3 is 2 kg/cm²G. The flow rates are regulated to: N₂=1 SLM(liter/minute in a standard state), H₂=0.2—1 SLM, and O₂=0.5—1 SLM. Theinternal pressure of the process chamber C is adjusted to 1 Torr by thevacuum pump RP. The orifice used as pressure reducing means RM is 0.6 mmin diameter, and the temperature inside the reactor WVG for generatingmoisture is set at 350° C.

FIG. 2 is a graph showing the dependence of the pressure of the reactorfor generating moisture on N₂ gas flow rate. With the vacuum pump RPstopped and the valve V11 opened, the process chamber C is set at theatmospheric pressure. In this state, the equipment in FIG. 1 is purgedwith N₂ gas alone. When the flow rate of N₂ gas is increased in therange of 1,000 to 5,000 sccm, the pressure of the reactor will riselinearly in the range of about 900 to 1,900 Torr.

Since an orifice is installed as pressure reducing means RM, N₂ gas willstay to increase the pressure of the reactor as the flow rate of N₂ gasincreases, because the flow to the downstream side is regulated by theorifice. Because the pressure is increased with N₂ gas, it is expectedthat the other mixed gas will rise in pressure.

FIG. 3 is a graph showing the dependence of the pressure of the reactorfor the pressure of the process chamber C is set at 1 Torr by operatingvacuum pump RP. With the flow rate of H₂ gas fixed at 1,000 sccm, theflow rate of O₂ is increased up to 600-1,500 sccm.

Theoretically, the flow rate of O₂ gas to react with 1,000 sccm of H₂gas is 500 sccm, and the flow rate of generated moisture gas is 1,000sccm. In practice, however, reaction does not proceed exactly accordingto the theory. H₂ gas remains unreacted in a small quantity, and theflow rate of moisture gas is slightly smaller than 1,000 sccm. Toincrease the total pressure of H₂—O₂, the flow rate of O₂, which has noadverse effect, is increased.

As is evident from FIG. 3, if the flow rate of O₂ gas is increased inthe range of 600 to 1,500 sccm, the pressure of the reactor riseslinearly in the range of about 400 to 740 Torr. It is clear from FIG. 7that within this pressure range, the ignition point of hydrogen in thereactor is about 560° C., that is, about 210° C. higher than the settemperature of 350° C. in the reactor. Therefore, there is nopossibility that hydrogen will ignite in the reactor.

FIG. 4 is a graph showing the concentration of unreacted H₂ gas whilethe flow rate of O₂ gas changes as in FIG. 3.

Even if oxygen is supplied excessively in the moisture generationreaction as shown in FIG. 3, the quantity of unreacted H₂ is at mostsome 0.08 percent. Furthermore, the pressure in the reactor can bemaintained at a high level by the pressure reducing means of the presentinvention. Thus, the ignition point rises, which definitely keepshydrogen from igniting and ensures that moisture can be produced safely.

In FIG. 1, an orifice is used as pressure reducing means RM. As analternative to that, a valve may be used. In case a valve is used, theflow rate ican be adjusted because the opening of the valve is variable.Thus, the pressure within the reactor for generating moisture can befreely adjusted. Also, any means that has a squeezing mechanism andpermits adjustment of pressure or produces pressure loss can be used aspressure reducing means RM, for example, nozzles, Venturi tubes,capillaries, and filters.

The present invention is not limited to the embodiments just described.It is to be understood that changes and variations may be made withoutdeparting from the spirit or scope of the present invention.

Embodiment of Heat Dissipation Reactor for Generating Moisture

FIG. 8 is a vertical, sectional view of the reactor shell of the reactorfor generating moisture according to the present invention. Theconstruction will be explained briefly. In FIG. 8, the same referencenumbers are used to refer to the same parts as in FIG. 5.

The reactor shell 1 comprises a reactor structural component 2 on theinlet side, a recess 2 a, a reactor structural component 3 on the outletside, a recess 3 a, welds 4, screw bolts 5, an interior space 6, amaterial gas supply passage 7, a reflector 8 on the inlet side, amaterial gas supply joint 9, a moisture gas outlet passage 10, areflector 11 on the outlet side, a moisture gas take-out joint 12, aplatinum coated catalyst layer 13, a barrier coat 13 a, a platinum coat13 b, heat dissipation units 14, a heater 15 and a heater pressing plate16.

FIG. 9 is a top view of the heat dissipation unit 14, while FIG. 10 is asectional view taken on line I-I in FIG. 9. The heat dissipation unit 14which releases heat has a large number of heat dissipation fins 18disposed in parallel on the base plate. In the center, there is provideda through hole 19 for the joint. A cut 20 is made that extends from thethrough hole 19 for the joint to the upper side of fine base plate 17.At the four cornrs of the fin base plate 17, fixing bolt holes 21 aredefined that reach reactor structural components 2, 3.

The fin base plate 17 and heat dissipation fins 18 are formed roughlycentral symmetrically with the through hole 19 for the joint serving ascenter.

In FIG. 9, the fin formation is not perfectly but roughly centralsymmetrical because the cut 20 is formed in unit 14. Because of thisroughly central symmetry, the heat dissipation of the heat dissipationunit 14 exhibits a central symmetry.

The unit is so designed that, because of this central symmetry, thetemperatures at two different points equally distant from the center andlocated on the same diametric line are about the same. If the heatdissipation characteristics of the reactor structural components 2, 3are made central symmetric, then the temperature distribution in theInterior space 6 of FIG. 6 also can be made central symmetric. Moisturegeneration reaction can be equalized central symmetrically, and thus thetemperature in the reactor shell 1 can be prevented from rising locally,In other words, this prevents hydrogen gas and oxygen gas from locallyigniting, thus promoting the safety of the reactor for generatingmoisture and prolonging the life of the reactor.

FIG. 11 is a side view of the reactor for generating moisture with theheat dissipation unit clamped on the reactor structural component on theinlet side. FIG. 8 is a section taken on line II-II in FIG. 11.

To attach the heat dissipation unit 14 (FIG. 10) on the reactorstructural component 2 on the inlet side, the material gas supply joint9 is first inserted through the through hole 19 for the joint, and thefin base plate 17 is closely placed on the outside wall of the reactorstructural component 2 on the inlet side. Then, bolts (not shown) arescrewed in and tightened up through the fixing bolt holes 21.

To attach the heat dissipation unit 14 on the reactor structuralcomponent 3 on the outlet side, the moisture gas take-out joint 12 isfirst inserted through the heater 15, the heater pressing plate 16 andthe through hole 19 for the joint. Then, the fin base plate 17 is placedclosely on the heater pressing plate 16, and bolts are screwed in andtightened up through the fixing bolt hole 21.

The inventors conducted intensive research in seeking to raise the heatdissipation efficiency of the heat dissipation unit 14, and found thatthe heat dissipation can be improved by giving an alumite treatment tothe surfaces of the heat dissipation fins 18.

Alumite treatment generally means formation of a thin oxide film onaluminum or aluminum alloy. Colored alumite treatment is now possible.Alumite treatment is generally applied to increase the resistance tocorrosion and wear. The inventors found that alumite treatment iseffective in improving heat dissipation.

The larger the area of alumite treatment, the greater the heatdissipation of the heat dissipation unit 14 is. Therefore, it ispreferable to give an alumite treatment not only to the surfaces of heatdissipation fins 18 but also to the surface of the fin base plate 17.

To compare the alumite treated heat dissipation fins and the untreatedfins in heat dissipation, the inventors tested three kinds of reactorsfor generating moisture—one with alumite treated heat dissipation fins,another having fins with no aluminite treatment, and still anotherwithout heat dissipation fins.

FIG. 12 is an end view of the reactor structural component 3 on theoutlet side. The reactor structural component 3 on the outlet side washoled at five points. The five holes were drilled at intervals of 1 cmstarting with a point 1 cm away from the center. Five thermocouple P₁-P₅for measurement of temperature distribution were put each 1 mm away fromthe inside wall to measure the temperature distribution in the radialdirection in the interior space 6 on the downstream side. Furthermore, athermocouple P for temperature regulation to measure the temperature onthe downstream side was inserted at a point 3 cm away from the perimeterso as to see how much the temperature was different from the settemperature of the heater 15. Also, the temperature on the upstream sidewas measured at the corresponding point on the reactor structuralcomponent 2 on the inlet side.

With H₂/O₂ set at 10/6, or with excessive supply of oxygen, moisture wasproduced in the oxygen rich state. That is because the oxygen rich stateincreases the moisture generation efficiency and reduces unreactedmaterial gases. The measurement results are shown in Table 1.Measurements of thermocouple P₁ are not given in the table. (See Table1).

As shown in Table 1, the temperatures on the downstream side almostagree with the set temperatures, which indicate that the heater 15 worksaccording to the regulated and set temperature. The temperature isregulated and set to send generated water vapor to the subsequentfacilities. The temperature is set at 300° C. as an example. It is alsopointed out that the temperature on the upstream side is lower than thaton the downstream side. That indicates that moisture generation hardlytakes place in the interior space 6 on the inlet side.

In the interior space 6 on the outlet side, moisture generation reactionis caused by the platinum catalyst, and therefore, the temperatures aredistributed, high around the edge to low in the center. Of thethermocouple P₂-P₅, thermocouple P₄, which 4 cm away from the center,shows the highest temperature. It means that moisture generation or heatis liable to concentrate at that position. That is because the higherthe moisture generation is, the larger the self-heating is. It isunderstood that the unit for the quantity of moisture generation is SLM,or liter/minute in the standard state.

TABLE 1 Measurement results of temperature in reactor for generatingmoisture (1) Temperature Temperature Temperature Temperature (° C.) at a(° C.) at a (° C.) at a (° C.) at a Temperature Temperature point P₅point P₄ point P₃ point P₂ P (° C.) on P (° C.) on Set 5 cm from 4 cmfrom 3 cm from 2 cm from Gas upstream Downstream Temperature downstreamdownstream downstream downstream Reactor (SLM) side side (° C.) centercenter center center Without fins N₂ 1 238 302 300 277 283 290 295 H₂O 1315 376 — 380 384 377 371 H₂O 1.5 390 471 — 478 484 474 466 With heat N₂1 198 302 300 274 282 290 295 dissipation fins H₂O 2 287 406 — 427 436418 403 disposed in parallel H₂O 2.5 327 467 — 491 502 481 464 (withoutalumite treatment) With heat N₂ 1 210 351 350 314 326 336 343dissipation fins N₂ 1 184 302 300 270 280 289 295 disposed in parallelH₂O 2 234 356 — 379 389 369 353 (with hard alumite H₂O 2.5 265 411 — 435448 426 407 20 μm thick) H₂O 3 295 466 — 493 509 482 461

If the upper limit temperature for safe operation of the reactor forgenerating moisture is 450° C., for example, the quantity of moisturegeneration where thermocouple P₄ indicates a temperature below 450° C.can be regarded as the quantity within the safe operation range.

Therefore, the upper limits of moisture generation for the respectivereactors are: the reactor without fins=1 SLM, the reactor with untreatedfins=2 SLM, and the reactor with hard alumite-treated fins=2.5 SLM. Inother words, provision of fins can increase moisture generation twice,and provision of alumite-treated fins can raise moisture generation 2.5times.

The above-mentioned alumite is a hard alumite 20 μm thick. Tests werealso conducted with colored alumite (black) 20 μm thick and hardalumites 5-50 μm. They made little difference. That is, readings ofthermocouple P₂-P₅ were varied only within several degrees.

In Table 2, temperatures are measured in the reactor for generatingmoisture with different thicknesses of alumite and different kinds ofalumite with the moisture generation at 2.5 SLM. (See Table 2).

To summarize, heat dissipation fins are effective in dissipating heatand narrowing the temperature distribution. The moisture generation canbe increased about twice.

It is also noted that alumite treatment on heat dissipation fins canimprove heat radiation rate. That is, the temperature can be lowered bysome 50° C. in comparison with the fins having no alumite treatment. Andthe moisture generation can be increased some 2.5 times.

The results shown in Table 1 are for heat dissipation fins disposedcentral symmetrically as shown in the drawing. The same results can beobtained with heat dissipation fins disposed roughly axialsymmetrically. It is understood that axial symmetry means a concentricarrangement of heat dissipation fins. In the axial symmetricalarrangement, the aforesaid temperature distribution will also be axialsymmetrical, which can enhance evenness in the interior space 6 formoisture generation.

TABLE 2 Measurement results of temperature in reactor for generatingmoisture (2) Temperature (° C.) Temperature (° C.) Temperature (° C.)Temperature (° C.) at a point P₅ 5 cm at a point P₄ 4 cm at a point P₃ 3cm at a point P₂ 2 cm Thickness and kind from downstream from downstreamfrom downstream from downstream of alumite Gas (SLM) center centercenter center Hard alumite  5 μm H₂O 2.5 439 453 429 412 Hard alumite 10μm H₂O 2.5 437 451 428 410 Hard alumite 15 μm H₂O 2.5 436 451 427 409Hard alumite 50 μm H₂O 2.5 435 448 425 406 Colored alumite 20 μm H₂O 2.5433 445 424 405

The present invention is not limited to the embodiment and examples justdescribed and it is to be understood that changes and variations may bemade without departing from the spirit or scope of the presentinvention.

Effects of the Invention

The invention has the following advantageous effects:

-   -   Hydrogen gas can be reduced in pressure by pressure reducing        means provided on the downstream side of the reactor for        generating moisture before being supplied to the downstream        side.    -   Ignition of hydrogen can be prevented without fail and,        therefore, a safe and stable supply of moisture can be provided        because the internal pressure in the reactor can be maintained        at a high level.    -   The pressure reduction and ignition prevention can be effected        by such simple pressure reducing means as an orifice. In case a        valve is used as pressure reducing means, it is possible to vary        and adjust the opening and also the degree of ignition        prevention.    -   Unreacted hydrogen contained in moisture gas can be minimized,        which further enhances the safety along with the pressure        reducing means, because the platinum coated catalyst layer        causes hydrogen and oxygen to react into moisture with a high        efficiency.    -   The temperature in the reactor shell can be lowered by        dissipating moisture generation heat through heat dissipation        fins, and the quantity of moisture generation can be increased.    -   Moisture generated by maintaining the temperature in the reactor        shell at a proper level with a heater can be led out as stable        water vapor flow to the subsequent facilities.    -   The temperature distribution in the reactor can be made        centrally or axially symmetrical, preventing the temperature        from rising locally and effecting safe and smooth moisture        generation in the reactor shell, because heat dissipation fins        are disposed roughly centrally or axially symmetrical.    -   The temperature in the reactor shell can be further lowered and        therefore the moisture generation can be further increased,        because the surfaces of heat dissipation fins are        alumite-treated to improve heat dissipation.

1. An apparatus for generating and feeding moisture, comprising: areactor having an upstream gas inlet side, a downstream moisture outletside and a catalyst for generating moisture from hydrogen and oxygen,wherein the reactor generates moisture from hydrogen and oxygen bycatalytic reaction at a temperature of not higher than 450° C.; meansfor reducing pressure provided on the downstream side of the reactor,and disposed so that moisture leaving and fed from said reactor isreduced in pressure by the means for reducing pressure while an internalhigh pressure in the reactor is maintained, wherein the means forreducing pressure comprises one or more components selected from thegroup consisting of an orifice, a valve, a capillary and a filter; afirst reactor structural component having a material gas supply jointdefining a material gas supply passage; a second reactor structuralcomponent having a moisture gas take-out joint defining a moistureoutlet passage, wherein the first reactor structural component and thesecond reactor structural component are mated to form a reactor shellhaving an interior space, and wherein the second reactor structuralcomponent defines an inside wall surface; a first reflector having anouter edge and disposed in the interior space to face the material gassupply passage; a second reflector having an outer edge and disposed inthe interior space to face the moisture outlet passage, wherein thefirst reflector and the second reflector are identical flat platessymmetrically disposed in the interior space, and the first reflectorand the second reflector each include a beveled peripheral portioninclined in cross-section; wherein the beveled peripheral portion issuch that a distance between each first or second reflector and itsrespective closest first or second structural component is increasing ina direction towards the outer edge of the reflector; wherein thecatalyst comprises a platinum coated catalyst layer provided on theinside wall surface of the second reactor structural component; and aprocess chamber, wherein the reactor is connected to feed moisture gasto the process chamber, wherein the moisture gas fed into the processchamber is reduced in pressure by the means for reducing pressure.
 2. Anapparatus for generating and feeding moisture according to claim 1,wherein internal pressure within the process chamber is 1-100 Torr. 3.An apparatus for generating and feeding moisture according to claim 1,wherein the second reflector is clamped by bolts to the inside wallsurface of the second reactor structural component.
 4. An apparatus forgenerating and feeding moisture, comprising: a reactor having anupstream gas inlet side, a downstream moisture outlet side and acatalyst for generating moisture from hydrogen and oxygen, wherein thereactor generates moisture from hydrogen and oxygen by catalyticreaction at a temperature set in the range of 300° C. to 450° C.; meansfor reducing pressure provided on the downstream side of the reactor,and disposed so that moisture leaving and fed from said reactor isreduced in pressure by the means for reducing pressure while an internalhigh pressure in the reactor is maintained, wherein the means forreducing pressure comprises one or more components selected from thegroup consisting of an orifice, a valve, a capillary and a filter; afirst reactor structural component having a material gas supply jointdefining a material gas supply passage; a second reactor structuralcomponent having a moisture gas take-out joint defining a moistureoutlet passage, wherein the first structural component and the secondstructural component are mated to form a reactor shell having aninterior space, and the second structural component defines an insidewall surface; a first reflector having an outer edge and disposed in theinterior space; a second reflector having an outer edge and disposed inthe internal space to face the moisture outlet passage, wherein thefirst reflector is disposed in the internal space to face the materialgas supply passage, and the first reflector and the second reflector areidentical flat plates symmetrically disposed in the interior space, andthe first reflector and the second reflector each include a beveledperipheral portion inclined in cross-section; wherein the beveledperipheral portion is such that a distance between each first or secondreflector and its respective closest first or second structuralcomponent is increasing in a direction towards the outer edge of thereflector; wherein the catalyst comprises a platinum coated catalystlayer provided on the inside wall surface of the second reactorstructural component; and a process chamber, wherein the reactor isconnected to feed moisture gas to the process chamber, wherein themoisture gas fed into the process chamber is reduced in pressure by themeans for reducing pressure.
 5. An apparatus for generating and feedingmoisture according to claim 4, wherein the second reflector is clampedby bolts to the inside wall surface of the second reactor structuralcomponent.